Recently, various types of cameras such as a zoom lens equipped camera, a multi-focus camera in which a plurality of focal lengths may be preset and a system camera in which various zoom lenses are exchangeable have been put on the market. Together with this, a camera having a zoom flash mounted thereon in which the flash illumination angle may be continuously changed has also been put on the market. Such means for changing the flash illumination angle of a zoom flash unit is disclosed in, for example, Japanese Unexamined Utility Model Publication Sho/No. 53-62330 and Japanese Unexamined Patent Publication Sho/No. 63-2030.
A photographic flash device disclosed in the Japanese Unexamined Utility Model Publication Sho/53-62330 comprises a main body, illumination angle changing means which is slidably disposed on the main body to cover the front part of a light emitting portion of the main body and having an optical lens secured to the front part thereof, and a sliding member which is actuated from outside of the main body for causing the illumination angle changing means to slide forwardly or rearwardly to a desired position and to hold the same there. The flash illumination angle may be changed by moving a condenser lens of a flash along an optical axis.
A lens shutter type zoom lens camera disclosed in the Japanese Unexamined Patent Publication No. 63-2030 comprises a powered zoom lens system which is a taking lens system, a magnification variable view finder optical system and an illumination angle variable flash unit which are interlocked with the zooming operation. A single cam plate is disposed above the view finder optical system and the flash unit. The cam plate is movable in a direction normal to the optical axis of the taking lens. The cam plate is formed with cam grooves for moving the magnification variable lens group of the magnification variable view finder optical system and a light-emitting tube of the variable illumination angle flash unit. The cam plate is interlocked with the zooming operation to be moved in a direction normal to the optical axis. Accordingly a simple structure using a single cam plate makes it possible to interlock the cam plate with the zooming operation for changing the field of view of the view finder and for moving the light emitting portion including a light emitting tube and a reflector of the flash unit to change the flash illumination angle.
As mentioned above, in the Japanese unexamined Utility Model Publication Sho/No. 53-62330 and the Japanese Unexamined Patent Application Sho/No. 63-20,30 the condenser lens of the flash is moved along the optical axis and the light-emitting portion is moved along the optical axis, respectively on changing the illumination angle of the flash in response to the focal length of the taking lens. The flash device disclosed in these publications inevitably invites complication and large size of an illumination angle changing mechanism since it is necessary to provide a mechanism for driving a condenser lens and a reflector mirror and a space in which the condenser lens and a reflector are movable along an optical axis. As a result of this, the accessory zoom flash unit which is to be mounted on a flash shoe of a camera is low in portability due to its large-size and the built-in flash which is disposed in the camera invites large-size of the whole of the camera, complication of a pop-up mechanism for preventing a red-eye effect which will be described below and a short length of the pop-up (height) movement due to the complication of the pop-up mechanism.
Considering the performance of the current zoom flash, there are restrictions imposed on largely changing the flash illumination angle by moving the condenser lens or the reflector mirror in the direction of an optical axis within a restricted space. The range of the flash illumination angle which may be changed without generating irregularly distributed light spots and lowering of the light amount at the periphery of a picture plane is limited in such a manner that the guide number converted from the illumination brightness in the center of the picture plane at a narrow illumination angle is about 1.2 to 1.3 times that at a wide illumination angle.
The recent high magnification zoom lens has a tendency that the f-number at a full aperture on the telephoto side is approximately one step larger than that on the wide-angle side for miniaturization. However, in general a distant object is often photographed on the telephoto side. As a result of this, it is uneasy to use a camera when a recent zoom-flash is used since the object distance at which flash photography is possible at a proper light amount is shorter on the telephoto side than on the wide angle side.
If the illumination angle of the flash is largely changed without generating irregularly distributed light dots and lowering the light amount at the peripheral area of the picture frame, it would be necessary to dispose a number of magnification variable condenser lenses in front of the flash reflector mirror. As a result of this, loss of the amount of light will increase due to transmission of light through a number of lenses and the volume necessary for the condenser lens will also increase so that the zoom flash unit will not become practical.
Therefore, it is an object of the present invention to provide a compact flash device for a camera having a simple mechanism which is capable of largely changing the illumination angle of the flash light-emitting portion in response to the focal length of a taking lens and in which the size of the electric circuit for the flash device is reduced.
It is another object of the present invention to provide a compact flash device for a camera having a simple mechanism, which is capable of largely changing the illumination angle of the flash in response to the focal length of a taking lens and is capable of generating a high guide number flash and is capable of reducing the occurrence of red-eye phenomenon.
In an aspect of the present invention, there is provided a flash device for a camera comprising: a plurality of flash light emitting portions having different flash illumination ranges; and control means responsive to the focal length of a taking lens of the camera for selectively firing one of the plurality of flash light emitting portions.
The control means may select a flash light emitting portion of a plurality of the flash light emitting portions, having a wide flash illumination range for firing the same when an object distance is smaller than a given distance.
The flash device for a camera may further include single power supply means for supplying electric power to a plurality of the flash light emitting portions; and a plurality of trigger means for activating each of a plurality of the flash light emitting portions to fire the same. The control means is adapted to select one of the trigger means to fire one of the plurality of the flash light emitting portions.
A flash light emitting portion of a plurality of the flash light emitting portions having a narrower illumination range may be disposed at a position farther from an optical axis of the taking lens than the other flash light emitting portions.
A plurality of the flash light emitting portions may be juxtaposed in a linear direction which perpendicularly intersects an optical axis of the taking lens.
A plurality of the flash light emitting portions may be juxtaposed in a height direction of a body of the camera.
A plurality of the flash light emitting portions may be enabled to emit light when they are in a position extending from the upper surface of the camera body.
The control means may obtain focal length information from a focal length detecting means disposed at the taking lens.
The control means may obtain object distance information from means for detecting a focussed position of a taking lens.
A flash light emitting portion of a plurality of said flash light emitting portions, having a wider flash illumination range may be disposed at a position farther from an optical axis of the taking lens than the other flash light emitting portions.
In another aspect of the present invention, there is provided a method of controlling light emission of a plurality of flash light emitting portions of a flash device having different illumination ranges comprising the steps of: determining whether or not the flash light emitting portions are enabled to fire; determining whether or not the focal length of a taking lens is longer than a given focal length; selecting a flash light emitting portion having a smaller flash illumination range for firing the same when the focal length is longer than a given focal length; and selecting a flash light emitting portion having a wider illumination range for firing the same when the focal length of the taking lens is shorter than a given focal length.
The method may further include a step for selecting a flash light emitting portion having a wide illumination range for firing the same when the focal length of the taking lens is longer than a given focal length and the object distance is smaller than a given distance.